Normal Duration of Menstrual Flow
Normal menstrual flow lasts 3 to 7 days, with the average being approximately 6 days. 1, 2
Evidence-Based Duration Parameters
The typical range is 3-7 days of bleeding per menstrual cycle, as documented in research examining normal menstrual patterns in women without subfertility 1
The mean duration is 6.2 days (median 6 days) based on prospective data from 581 women tracked over 3,324 menstrual cycles 2
Bleeding lasting 8 days or longer is considered abnormal and warrants further evaluation, according to pediatric and adolescent health guidelines 1
Clinical Context for Flow Duration
Normal cycle length ranges from 21-45 days in adolescents and 26-35 days in adult women, providing context for when the 3-7 day bleeding window occurs 1, 3
Within-woman variability exists: approximately 11.6% of women show differences of more than 3 days between their longest and shortest menses length over the course of a year 2
When Menstrual Flow Duration Becomes Clinically Significant
Menses lasting ≥8 days requires evaluation for potential pathology such as fibroids, polyps, bleeding disorders, or endometrial abnormalities 1
For women with endometriosis, flow duration may be slightly longer (mean difference of 0.33 days) compared to women without the disease 4
NSAIDs should be used for 5-7 days during menstruation when treating heavy or prolonged bleeding, which aligns with the normal duration window 5, 6
Important Clinical Pitfall
Do not assume that subjective patient assessment of flow duration or volume is accurate. Research demonstrates that 92% of women with objectively heavy menstrual flow (above the 95th percentile) underrate their bleeding as "normal" on subjective evaluation 7. This highlights the importance of using objective measures when clinically indicated rather than relying solely on patient perception.